1. Statement of the Technical Field
The inventive concepts relate to sensors for measuring physical forces and torques.
2. Description of Related Art
Force and torque sensors are commonly used to determine the physical forces and torques, i.e., moments, acting on a mechanical element or structure. Force and torque sensors typically include a load-bearing element, or flexure, and a plurality of strain gauges mounted on the flexure. The sensor is mounted so that the flexure is subjected to the forces and moments to be measured. The forces and moments, when applied to the flexure, induce deflection, or strain, in the flexure. Because the strain gauges are mounted on the flexure, the strain gauges themselves undergo strain in response to the strain experienced by the flexure, and the strain gauges generate outputs responsive to this strain. These outputs can be correlated to the magnitudes of the forces and moments acting on the flexure through predetermined data developed though a calibration process conducted on the sensor.
Force and torque sensors capable of measuring forces and torques acting in multiple directions typically include a relatively large number of active strain gauges, e.g., six axis force/torque sensors often include twenty or more. The use of a large number of strain gauges is typically necessary in order to allow the sensor to compensate for strain in the flexure induced by changes in the temperature of the flexure. However, the use of a large number of strain gages makes the sensors more complex, costly, and difficult to manufacture. Moreover, the flexures of such multi-axis sensors often have complex geometries in order to accommodate the strain gauges in specific orientations needed to measure multi-dimensional strain of the flexure. The complex flexure design can drive the overall size and weight of the flexure to undesirably high levels. Conversely, in applications where the flexure must be downsized in order to measure relatively small forces and torques, the complex geometry of the flexure may result in portions of the flexure being excessively thin or otherwise non-robust, which in turn can adversely affect the reliability and life of the flexure.